The Contractor shall exert its best efforts to: Develop methodologies and approaches which are expected to have wide application in studies of macromolecules present at cell surfaces. Correlate these studies from the standpoint of both structure and function. The model system used shall be the TL antigen system of the mouse; work undertaken shall include antigen preparttion and purification and relevant biochemical studies; and develop new, sensitive microchemical methods suitable for use in characterization of cell surface antigens.